Background: Most reports on the results of the Bernese periacetabular osteotomy for the treatment of developmental dysplasia of the hip have been by the originators of the procedure. In 1997, we began to use this osteotomy without direct training from the originators of the procedure.
Methods: Seventy-three patients (eighty-three hips) underwent a Bernese periacetabular osteotomy between 1997 and 2003 and were followed prospectively with use of the Harris hip score to assess clinical results and with use of anteroposterior pelvic and false-profile lateral plain radiographs to assess radiographic results. The three-dimensional position of the acetabulum was recorded preoperatively and postoperatively. The mean duration of follow-up was forty-six months.
Results: The average Harris hip score improved from 54 to 87 points (p < 0.001). Three hips (three patients) had a conversion to total hip arthroplasty at two, three, and four years after the periacetabular osteotomy. Preoperatively, fifty-four of the eighty-three acetabula were anteverted, and twenty-nine were either retroverted or had neutral wall relationships. Postoperatively, sixty-five hips (78%) were anteverted. Radiographically, in preoperatively anteverted hips, the average center-edge angle improved from 3° to 29° (p < 0.0001), the average anterior center-edge angle improved from 5° to 31° (p < 0.0001), and the acetabular index improved from 25° to 5° (p < 0.0001). In preoperatively retroverted or neutral hips, the average center-edge angle improved from 13° to 33° (p < 0.0001), the average anterior center-edge angle improved from 15° to 36° (p < 0.0001), and the acetabular index improved from 19° to 2° (p < 0.0001). Complications included four hematomas, three transient femoral nerve palsies, two deep wound infections, and one transient sciatic nerve palsy. Nine of the ten major complications and all four of the failed osteotomies occurred in the first thirty hips in which the index procedure was performed.
Conclusions: In our experience, the early results of the Bernese periacetabular osteotomy have been encouraging, with a 92% survival rate at thirty-six months. The occurrence of complications demonstrates a substantial learning curve. Recognition of the true preoperative acetabular version and reorientation of the acetabulum into an appropriately anteverted position have become important factors in surgical decision-making.
Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.
1 Department of Orthopaedics, University of Utah, 590 Wakara Way, Salt Lake City, UT 84108. E-mail address for C.L. Peters: Chris.Peters@hsc.utah.edu
Redirectional acetabular osteotomy has been performed at our institution since the early 1970s. Prior to 1997, the favored osteotomy for patients with developmental dysplasia and nonarthritic hips was the triple innominate osteotomy as described by Steel1,2. As our nine-year follow-up showed a 27% rate of conversion to total hip arthroplasty, substantial perioperative morbidity, and postoperative limp in these patients3,4, we began to use the Bernese periacetabular osteotomy in 1997 because of its purported advantages.
The advantages of the Bernese periacetabular osteotomy include a single incision and osteotomies that are performed close to the joint, allowing for large corrections of the acetabulum. In addition, the maintenance of an intact posterior column preserves the intrinsic stability of the pelvis5. Since the introduction of the Bernese periacetabular osteotomy, the clinical and radiographic results of this procedure have been reported pre-dominately by the Berne group, by surgeons who have trained in Berne, or for small series of patients with unusual diagnoses other than developmental dysplasia of the hip5-29. To our knowledge, a consecutive series of periacetabular osteotomies performed by a single surgeon who was not trained in Berne has not been reported in the English-language literature.
The purpose of the present report is to describe the early clinical and radiographic results for a consecutive series of patients in whom the Bernese periacetabular osteotomy was performed by a single surgeon for the treatment of symptomatic acetabular dysplasia. Because the series represents our learning curve, we wished to determine if our surgical technique, results, and avoidance of complications improved with time. Finally, because of the recent recognition of the importance of assessing acetabular version, we wanted to critically examine the preoperative and postoperative three-dimensional positions of the acetabulum in our patients.
Materials and Methods
This retrospective study was approved by our institutional review board. Between 1997 and 2003, seventy-three patients (eighty-three hips) underwent consecutive periacetabular osteotomies that were performed by the senior author (C.L.P.). Although experienced in the anatomy of the pelvis and pelvic redirectional osteotomy after having performed more than thirty Steel innominate osteotomies, the senior author learned the periacetabular osteotomy procedure by first assisting another surgeon who was experienced with the procedure during multiple operations and then by performing the operation on four cadavers with the assistance of the same experienced surgeon. The experienced surgeon then assisted the senior author during the first several operations in this series. In 2001, after several years of performing the periacetabular osteotomy, further refinement and understanding of the procedure were obtained during several visits, including those in which the senior author assisted one of the originators of the operation during surgery.
Follow-up data were obtained prospectively with a clinical questionnaire and at yearly physical and radiographic examinations. The patient population consisted of fifty-five female patients and eighteen male patients with an average age of twenty-eight years (range, fifteen to forty-seven years). The average height was 65 in (165 cm), and the average weight was 171 lb (78 kg). The average body mass index was 28.5 (range, 17.1 to 33.9). Nine patients had had at least one previous operation on the hip: four patients had had one previous operation, and five had had multiple operations (range, two to fifteen operations). Previous procedures included open reduction or soft-tissue release, pinning of a slipped capital femoral epiphysis, corrective osteotomy of the femur, and hip arthroscopy. Patients who had had a previous pelvic osteotomy were excluded from the study. Seven female patients and three male patients underwent a bilateral staged procedure. Forty-three periacetabular osteotomies were performed on the right side, and forty were performed on the left side.
The preoperative diagnosis was “classic” acetabular dysplasia (characterized by an anteverted acetabulum with deficiency in anterior and lateral coverage of the femoral head) in fifty-nine hips, acetabular dysplasia with retroversion (characterized by deficient posterior coverage and relative anterior overcoverage of the femoral head) in twenty-two hips (Fig. 1), and acetabular dysplasia with concomitant Legg-Calvé-Perthes disease in two hips. A periacetabular osteotomy alone was performed in sixty-nine hips, a periacetabular osteotomy with a varus proximal femoral osteotomy was performed in eleven, a periacetabular osteotomy with a valgus proximal femoral osteotomy was performed in two, and a periacetabular osteotomy with relative femoral neck lengthening was performed in one.
All patients in our series had a preoperative magnetic resonance imaging study. In addition, magnetic resonance arthrography has been utilized routinely by us since 2001 to facilitate the diagnosis of labral or chondral injury.
The Bernese periacetabular osteotomy5,7-9 was performed through a modified Smith-Petersen approach with the patient lying in the supine position on a radiolucent table. The abductor muscles were left intact on the lateral aspect of the ilium. Image intensification was used for the ischial, pubic, and iliac osteotomies as well as for confirmation of final acetabular positioning and fixation.
Judgment of final acetabular positioning was performed by first adjusting the angle of the image intensifier to ensure that the tip of the coccyx was 2 to 5 cm cephalad to the symphysis pubis and the rotation of the pelvis was neutral. Superolateral coverage and anteversion were then estimated with two-plane image intensification. Our radiographic criteria for optimum placement of the osteotomized acetabulum were a horizontal sourcil and appropriate acetabular anteversion, manifested by a posterior wall extending lateral to the center of the femoral head and an anterior wall extending medial to the center of the femoral head (Fig. 1). Since the preoperative version of the acetabulum was different for each patient, the optimum placement of the osteotomized acetabular fragment was individualized. Fixation was accomplished with three, four, or five large or small-fragment cortical screws.
A combined general and epidural anesthetic was administered during seventy-two of the eighty-three procedures. The mean estimated blood loss was 715 mL (range, 100 to 2500 mL). No drains were used. The anticoagulation regimen included enoxaparin and compression boots. The administration of enoxaparin was avoided for twelve hours before removal of the epidural catheter and was delayed by at least four hours after removal of the epidural catheter. At the time of discharge from the hospital, patients were managed with aspirin for six weeks. Partial weight-bearing with two crutches was encouraged for six weeks, and then full weight-bearing with one crutch or a cane was encouraged for six weeks until walking could be accomplished without a limp (generally at three months).
Prior to 2001, arthrotomy of the hip was performed only when preoperative magnetic resonance imaging revealed evidence of acetabular labral abnormality. Beginning in 2001, with the thirty-fourth case of our series, arthrotomy of the hip was performed routinely. Overall, arthrotomy of the hip was performed in conjunction with periacetabular osteotomy in forty-nine hips (59%). Partial labral excision was performed in eleven hips, and an osteochondroplasty of the femoral head-neck junction was performed to improve femoral head-neck offset in thirty-five hips. Osteochondroplasty was performed if there was abutment of the femoral head-neck junction against the newly positioned anterior acetabular rim with ≤90° of hip flexion and ≤20° of internal rotation of the femur or if there was obvious overgrowth at the femoral head-neck junction resulting in loss of normal head-neck offset.
The Harris hip score was determined preoperatively, at six months and one year postoperatively, and yearly thereafter. A physician assistant (J.A.E.) who is a member of our adult reconstruction service performed the clinical evaluations.
The preoperative, six-week, six-month, and yearly postoperative radiographs included an anteroposterior pelvic and false-profile lateral radiograph for all patients. A preoperative radiograph made with the hip in abduction and internal rotation was made to assess whether a concentric reduction of the femoral head could be achieved4.
Radiographs were evaluated by measuring the acetabular index4, the center-edge angle30, the anterior center-edge angle4, and the acetabular angle of Sharp4.
Radiographs also were evaluated for congruence of the femoral head in the acetabulum as well as for acetabular rim changes such as sclerosis and/or cyst formation. Beginning in 2001, the orientation of the acetabulum was routinely assessed for anteversion, retroversion, or neutral wall relationships preoperatively and postoperatively as described by Ganz et al.15,25,31.
The presence of osteoarthritis was graded on all radiographs according to the criteria of Tönnis32. The presence of any iliac, ischial, and pubic nonunions also was recorded on the yearly postoperative radiographs. The radiographic evaluation was performed by a physician assistant (J.A.E.).
All data were analyzed with use of a commercially available software package (FileMaker Pro 7.0 [FileMaker, Santa Clara, California] and Microsoft Excel [Microsoft, Redmond, Washington]). Comparisons were performed with use of the Student t test. The level of significance was set at p ≤ 0.05. Kaplan-Meier survival analysis was performed by an independent statistician, with revision of the osteotomy or conversion to total hip arthroplasty as the end point.
The mean duration of follow-up was forty-six months (range, thirty to eighty-eight months). The mean Harris hip score improved from 54 (range, 20 to 81) preoperatively to 86 (range, 49 to 100) at one year (p < 0.001) and to 87 (range, 49 to 100) at the time of the most recent follow-up (p < 0.001). The mean Harris hip score for the patients with a preoperatively anteverted acetabulum improved from 55 (range, 20 to 80) preoperatively to 87 (range, 49 to 100) at the time of the most recent follow-up (p < 0.001). The mean Harris hip score for the patients with a retroverted or neutral acetabulum improved from 54 (range, 25 to 76) preoperatively to 88 (range, 49 to 100) at the time of the most recent follow-up (p < 0.001).
Complications included three transient femoral nerve palsies, one transient sciatic nerve palsy, four hematomas, and two deep infections. In one patient, an osteotome tip broke within the ischium and was left in place. The patient remained asymptomatic. Two of the three femoral nerve palsies completely resolved within the first year; the third patient with this complication had residual weakness and numbness. The patient with the sciatic nerve palsy did not have symptoms preoperatively and remained mildly symptomatic with painful numbness but full motor function at the time of the most recent follow-up. The four hematomas were treated with irrigation and débridement. The two deep infections were treated with irrigation and dé-bridement and six weeks of intravenous antibiotics.
Four hips in four patients were considered to have had a failure, defined as conversion to total hip arthroplasty or revision osteotomy. Three hips had a conversion to total hip arthroplasty at two, three, and four years postoperatively because of pain and continued arthritic degeneration. Two of these three hips had undergone irrigation and débridement, one because of a hematoma and one because of a deep infection. The fourth patient who had a failure underwent revision periacetabular osteotomy (performed by another surgeon) because of pain and femoroacetabular impingement. All four of these hips were among the first thirty hips in our group that underwent the index procedure.
Kaplan-Meier analysis revealed a survival rate of 92% at thirty-six months with revision periacetabular osteotomy or conversion to total hip arthroplasty as the end point (Fig. 2).
In the last fifty-three hips that underwent the index procedure, there was only one complication (a transient femoral nerve palsy), which did not adversely affect an eventual good outcome. Thirteen femoral osteotomies were performed in combination with our first forty-one periacetabular osteotomies, and only one was performed in combination with our most recent forty-two periacetabular osteotomies.
All eighty-three hips had complete preoperative, postoperative, and follow-up radiographs. Preoperatively, fifty-four acetabula were anteverted and twenty-nine were retroverted or had neutral wall relationships. The preoperative and postoperative acetabular wall relationships are shown in Table I. Improvements in the various radiographic indices are shown in Table II.
The integrity of the Shenton line was broken in thirty-five of the eighty-three hips preoperatively, and it remained broken in thirty-seven hips postoperatively. The femoral head was not concentrically located in the acetabulum in thirty-seven of the eighty-three hips preoperatively, whereas only four hips exhibited a nonconcentric reduction postoperatively. Two of these hips (one in a patient with spastic cerebral palsy and the other in a patient with an aspherical femoral head) went on to subsequent total hip arthroplasty. The latter two patients continued to function well.
Radiographic evidence of osteoarthritis, as graded on the Tönnis scale, did not progress in fifty-eight of the eighty-three hips. Twenty-three hips had one grade of progression, and three had two grades of progression. In the three patients who went on to have a total hip arthroplasty, one had one grade of progression and two had two grades of progression (from I to III) before undergoing arthroplasty at three or four years postoperatively.
Ten nonunions of the pubis and one nonunion of the ischium were diagnosed radiographically. The one hip with an ischial nonunion also had a pubic nonunion and underwent a second operation for additional bone-grafting and fixation, with eventual union of both sites. Eight of the remaining nine pubic nonunions were asymptomatic at the time of the most recent follow-up, and most were in hips with large corrections. One of these nine pubic nonunions was symptomatic, but the patient did not wish to undergo a reoperation.
Our early results with the Bernese periacetabular osteotomy are of interest because none of the authors trained directly in Berne and the series represents our learning curve with what is considered to be a technically difficult operation5,7-9,33. Moreover, during this series, we incorporated newer knowledge into our evaluation and treatment regimen. For example, there recently has been increased recognition that the acetabulum may be retroverted or in neutral version in many patients with developmental dysplasia15,16,25,27,31. The prevalence of acetabular retroversion in our series is similar to that in the recent studies by Li and Ganz (232 hips) and Mast et al. (153 hips), who reported that as many as one-third of hips that underwent periacetabular osteotomy were preoperatively retroverted15,16. We now recognize the importance of determining the version of the acetabulum preoperatively and restoring normal anteversion with the osteotomy if possible. In addition, during the time of our series, there was increased recognition of the importance of concomitant labral abnormalities and descriptions of conditions that predispose the hip to femoroacetabular impingement27,34. Over the seven-year period of this series, we substantially changed our preoperative and intraoperative approach to identify and treat these problems as part of the periacetabular osteotomy procedure.
Beginning in 2001, critical analysis of the anterior and posterior acetabular wall relationships and recognition of the presence of femoroacetabular impingement became an important part of our preoperative evaluation and intraoperative plan. Our surgical goal for all periacetabular osteotomies is to place the acetabular fragment in an appropriately anteverted position and to improve femoral head-neck offset by means of osteochondroplasty of the femoral head-neck junction. Importantly, in hips with anteversion, which typically have a combined anterolateral deficiency of coverage, we correct the acetabular fragment to produce a horizontal sourcil with an anterior wall that is medial to the posterior wall of the acetabulum as seen on an anteroposterior radiograph of the pelvis (Fig. 1). In our series, fifty-four hips were anteverted preoperatively and 74% (forty) of these fifty-four hips were correctly positioned into anteversion postoperatively.
We correct the retroverted acetabulum, which typically has a deficiency of posterior coverage, relative anterior over-coverage, and a relatively horizontal sourcil, by moving the posterior wall lateral to the center of the femoral head with corresponding medial movement of the anterior wall while maintaining a horizontal sourcil. This anteversion maneuver improves anterior hip clearance, which may reduce the potential for femoroacetabular impingement. A retroverted acetabulum typically does not require enhancement of lateral acetabular coverage.
Postoperatively, twenty-five (86%) of the twenty-nine hips in our series that were retroverted or neutral preoperatively were correctly repositioned into anteversion. As we gained experience and were able to incorporate newer knowledge into our treatment regimen, we were able to more accurately redirect the acetabulum. Seventeen of the eighteen hips that were under-corrected, that is, those that had neutral wall relationships or acetabular retroversion on postoperative radiographs, were among the first thirty-four hips that underwent the index procedure. Only one of the last forty-nine hips to undergo the procedure was left in a retroverted or neutral position. This latter hip was in a patient who had spastic cerebral palsy and had undergone multiple previous hip operations. Overall, as emphasized by Siebenrock et al.27, a more thorough preoperative identification of the true three-dimensional position of the acetabulum has improved our ability to balance the dysplastic horseshoe-shaped acetabulum over the femoral head.
In the original description of the operation from the Berne group, most complications occurred in the first twenty hips that underwent the procedure5,28. Our data also reflect such a learning curve as all of the hips that had a failure were among the first thirty that underwent the procedure. Similarly, nine of the ten major complications, including transient femoral nerve palsy (two hips), sciatic nerve palsy (one hip), postoperative hematoma (four hips), and deep infection (two hips), occurred in the first thirty hips that underwent the procedure, while only one major complication occurred in the subsequent fifty-three hips that underwent the procedure. Furthermore, thirteen concomitant proximal femoral osteotomies were performed in the first forty-one hips that underwent the procedure, but only one femoral osteotomy was performed in the last forty-two hips that underwent the procedure. This finding reflects our increased level of comfort and ability to correct the dysplastic deformity with acetabular reorientation alone.
Eleven (22%) of the forty-nine hips in which an arthrotomy was performed showed evidence of labral abnormality. These findings are in agreement with the 21% rate of labral tears as reported by Siebenrock et al.28. In that series, patients with labral tears had a worse outcome28. However, at the time of the most recent follow-up, the average Harris hip score for the eleven patients with a known labral tear in our series was 90 points and none of these patients had radiographic signs of progression of arthrosis. The ultimate outcome for these patients and the optimal treatment of a torn labrum will require additional studies.
In summary, on the basis of our surgical experience and the incorporation of newer information regarding acetabular wall relationships, femoral acetabular impingement, and the importance of detecting and treating labral abnormalities, our preoperative evaluation routinely includes plain radiographs that are used to determine the version of the acetabulum and whether a congruent hip can be achieved with redirection. We now perform magnetic resonance arthrography for all patients to determine whether or not there is labral abnormality and to try to determine the integrity of the articular surfaces. We consider Tönnis grade-II (or greater) arthrosis, evidence of incongruity between the femoral head and the acetabulum on the preoperative abduction-internal rotation radiograph, and substantial acetabular articular cartilage degeneration on preoperative magnetic resonance arthrography as contraindications to periacetabular osteotomy.
Our current operative goal is to restore normal anatomic anteversion. We routinely perform arthrotomy, and, if a torn acetabular labrum is noted, we perform either a limited partial resection or, if the labrum is detached from the acetabular rim, we débride the rim to bleeding bone and reattach the labrum to the rim with use of suture anchors. If there is residual femoral acetabular impingement after appropriate repositioning of the acetabulum, we correct it by performing a chondro-osseous débridement of the femoral head-neck junction to allow for impingement-free movement with the hip in 90° of flexion and slight internal rotation. ▪
NOTE: The authors thank Jeff Mast, MD, and Peter Stevens, MD, for their teaching and guidance in the diagnosis and treatment of patients with hip dysplasia.
A commentary is available with the electronic versions of this article, on our web site () and on our quarterly CD-ROM (call our subscription department, at 781-449-9780, to order the CD-ROM).
The authors did not receive grants or outside funding in support of their research for or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
Investigation performed at the Department of Orthopaedics, University of Utah, Salt Lake City, Utah
1. . Triple osteotomy of the innominate bone. J Bone Joint Surg Am. 1973;55: 343-50.
2. . Triple osteotomy of the innominate bone. A procedure to accomplish coverage of the dislocated or subluxated femoral head in the older patient. Clin Orthop Relat Res. 1977;122: 116-27.
3. , Coleman SS, Biddulph G. Triple innominate osteotomy for acetabular dysplasia. J Pediatr Orthop. 1993;13: 426-30.
4. , Fukushima BW, Park TK, Coleman SS, Dunn HK. Triple innominate osteotomy in young adults for the treatment of acetabular dysplasia: a 9-year follow-up study. Orthopedics. 2001;24: 565-9.
5. , Klaue K, Vinh TS, Mast JW. A new periacetabular osteotomy for the treatment of hip dysplasias: technique and preliminary results. Clin Orthop Relat Res. 1988;232: 26-36.
6. , Barrett SE, Gordon JE, Delgado ED, Schoenecker PL. Periacetabular osteotomy for the treatment of severe acetabular dysplasia. J Bone Joint Surg Am. 2005;87: 254-9.
7. , Klaue K, Mast J. [Peri-acetabular reorientation osteotomy]. Acta Orthop Belg. 1990;56: 357-69. French.
8. , Klaue K, Vinh TS, Mast JW. A new periacetabular osteotomy for the treatment of hip dysplasias: technique and preliminary results. 1988. Clin Orthop Relat Res. 2004;418: 3-8.
9. , Leunig M. Osteotomy and the dysplastic hip: the Bernese experience. Orthopedics. 2002;25: 945-6.
10. , Kim YJ, Millis MB. Periacetabular osteotomy in patients with Down's syndrome. J Bone Joint Surg Br. 2005;87: 544-7.
11. , Beck M, Woo A, Dora C, Kerboull M, Ganz R. Acetabular rim degeneration: a constant finding in the aged hip. Clin Orthop Relat Res. 2003;413: 201-7.
12. , Ganz R. [The Bernese method of periacetabular osteotomy]. Orthopade. 1998;27: 743-50. German.
13. , Siebenrock KA, Ganz R. Rationale of periacetabular osteotomy and background work. Instr Course Lect. 2001;50: 229-38.
14. , Werlen S, Ungersbock A, Ito K, Ganz R. Evaluation of the acetabular labrum by MR arthrography. J Bone Joint Surg Br. 1997;79: 230-4. Erratum in: J Bone Joint Surg Br. 1997;79:693.
15. , Ganz R. Morphologic features of congenital acetabular dysplasia: one in six is retroverted. Clin Orthop Relat Res. 2003;416: 245-53.
16. , Brunner RL, Zebrack J. Recognizing acetabular version in the radiographic presentation of hip dysplasia. Clin Orthop Relat Res. 2004;418: 48-53.
17. , Trumble SJ, Mast JW. Results of periacetabular osteotomy in patients with previous surgery for hip dysplasia. Clin Orthop Relat Res. 1999;363: 73-80.
18. . The Bernese Periacetabular Osteotomy: review of reported outcomes and the early experience at the University of Iowa. Iowa Orthop J. 2003;23: 23-8.
19. , Kim YJ. Rationale of osteotomy and related procedures for hip preservation: a review. Clin Orthop Relat Res. 2002;405: 108-21.
20. , Murphy SB. [The Boston concept. Peri-acetabular osteotomy with simultaneous arthrotomy via direct anterior approach]. Orthopade. 1998;27: 751-8. German.
21. , Deshmukh R. Periacetabular osteotomy: preoperative radiographic predictors of outcome. Clin Orthop Relat Res. 2002;405: 168-74.
22. , Millis MB. Periacetabular osteotomy without abductor dissection using direct anterior exposure. Clin Orthop Relat Res. 1999;364: 92-8.
23. , Millis MB, Hall JE. Surgical correction of acetabular dysplasia in the adult. A Boston experience. Clin Orthop Relat Res. 1999;363: 38-44.
24. , Stark A, Wallensten R. Periacetabular osteotomy. Good pain relief in symptomatic hip dysplasia, 32 patients followed for 4 years. Acta Orthop. 2005;76: 67-74.
25. , Lucas J, Klaue K. Retroversion of the acetabulum. A cause of hip pain. J Bone Joint Surg Br. 1999;81: 281-8.
26. , Leunig M, Ganz R. Periacetabular osteotomy: the Bernese experience. Instr Course Lect. 2001;50: 239-45.
27. , Schoeniger R, Ganz R. Anterior femoro-acetabular impingement due to acetabular retroversion. Treatment with periacetabular osteotomy. J Bone Joint Surg Am. 2003;85: 278-86.
28. , Scholl E, Lottenbach M, Ganz R. Bernese periacetabular osteotomy. Clin Orthop Relat Res. 1999;363: 9-20.
29. , Ekkernkamp A, Ganz R, Wallrichs SL. Periacetabular and intertrochanteric osteotomy for the treatment of osteoarthrosis in dysplastic hips. J Bone Joint Surg Am. 1995;77: 73-85.
30. . Shelf operation in congenital dysplasia of the acetabulum and in subluxation and dislocation of the hip. J Bone Joint Surg Am. 1953;35: 65-80.
31. , Eijer H, Ganz R. Anterior femoroacetabular impingement after periacetabular osteotomy. Clin Orthop Relat Res. 1999;363: 93-9.
32. , Heinecke A. Acetabular and femoral anterversion: relationship with osteoarthritis of the hip. J Bone Joint Surg Am. 1999;81: 1747-70.
33. , Gill TJ, Gautier E, Ganz K, Krugel N, Berlemann U. Surgical dislocation of the adult hip a technique with full access to the femoral head and acetabulum without the risk of avascular necrosis. J Bone Joint Surg Br. 2001;83: 1119-24.
Copyright 2006 by The Journal of Bone and Joint Surgery, Incorporated
34. , Parvizi J, Beck M, Leunig M, Notzli H, Siebenrock KA. Femoroacetabular impingement: a cause for osteoarthritis of the hip. Clin Orthop Relat Res. 2003;417: 112-20.